Baking oven



D. J. BOAL.

June l5, 1954 BAKING OVEN www uw Mw vw Q6" www N. |w|||| m w A EEE @f Filed June 2. 1949 June 15, 1954 D. J. BOAL 2,681,017

BAKING OVEN Filed June 2. 1.949 3 Sheets-Sheet 2 m @wm QQQ INVENToR.

iQ DAVID J. Bom.

HIS A TT GRA/EY D. J. BOAL BAKING OVEN June 15, 1954 3 Sheets-Sheet 3 Filed June 2. 1949 Patented June 15, 1954 BAKING IOVEN David J. Boal, Philadelphia, Pa., assignor to Spivey Co. Inc., Philadelphia, Pa., a corporation of Pennsylvania Application June 2, 1949, Serial No. 96,745

11 Claims.

essential that all of the units in a transverse row shall be subject to identical baking conditions at any instant, although the row as a whole may be, and generally is subjected to a variety of baking conditions during the transit of the row throughout the length of the oven. Considerable diiiiculties have been heretofore experienced in the baking of transverse rows of products moved continuously or step by step through long ovens due to the pocketing of air and moisture and localized concentrations of heat resulting in the scorching of the units at the ends of the rows or to the unequal baking of the units in a row.

My invention is designed to overcome such difficulties by eifecting uniform distribution of the heat applied to a row at any given time and uniform withdrawal of moisture-laden air without the formation of eddies or pockets.

A further object of my invention is the withdrawal of air uniformly across the entire width of the baking band, and preferably of the oven, without obstructing air flow longitudinally of the oven or weakening the roof to an extent necessitating auxiliary supports for the air exhaust pipes.

A further object of my invention is the substantial elimination of overall expansion and contraction of the oven tunnel and the elimination of such stresses and strains on the tunnel walls as are commonly imparted thereto by longitudinal metallic beams in thermal proximity L,

to the baking band.

A further object of my invention is to cause the baking band tov run straight in direct contact with supporting rollers and avoid the skewing of the latter.

A further object of my invention is toprovide improved means for supporting a tensioning drum for the baking band and for guiding such band to the drum.

A further object of my invention is to increase efficiency by keeping the baking band out of thermal proximity to structural elements of high thennal conductivity during the major portion of its travel and by preheating the baking band shortly before the deposit of dough thereon.

In the preferred embodiment of my invention, a long tunnel is formed from a series of units each comprising panels of low thermal conductivity; certain of the top panels being recessed from side to side of the tunnel to form chambers having uniformly apertured oors and arched roofs supporting exhaust conduits for evacuating moisture laden air uniformly across the tunnel without the formation of eddies.

An endless baking band is mounted on driving and tensioning drums at opposite ends of the tunnel. The sections of the band between the drums runs through the tunnel and is supported thereon directly on cylindrical rollers engaging the full width of the band. The rollers are mounted on bearings which may be supported by longitudinal exterior beams or plates shielded by the tunnel walls from heat radiated from the baking bands. The skewing of the rollers by displacement of their bearings is thereby prevented and certain of the rollers are adjustable as a group to guide the returning lap of the band tangentially to the periphery of the tensioning drum notwithstanding changes in the length of the band due to expansion and consequent movement of the tensioning drum.

The principles of my invention and the best mode in which I have contemplated applying such principles will further appear from the following description and the accompanying drawing in illustration thereof.

In the drawings, Fig. l is a diagrammatic side elevation of a baking oven embodying my invention; Fig. 2 is an enlarged fragmentary top plan view of the oven shown in Fig. l taken substantially on the line 2-2 of Fig. 3, with parts.` omitted and other parts in section; Fig. 3 is a vertical longitudinal sectional View of parts of the oven shown in Fig. 2; Fig. 4 is an enlarged side elevation of an oven unit indicated in Fig. l, with parts broken away; Fig. 5 is a transverse vertical sectional view taken approximately on the line 5 5 of Fig. 4; Fig. 6 is a fragmentary horizontal Sectional View taken on the line -B of Fig. 5; Fig. '7 is a broken elevation of the inner side of one of the panels used forming side walls of each oven unit; Fig. 7A is a broken top plan view of the panel shown in Fig. 7; Fig. 8 is a plan View of the inner side of one of the panels used for forming the bottom and top of each oven unit; Fig. 8A is an edge view of the panel shown.-

in Fig. 8; Fig. 9 is an enlarged fragmentary View showing a side elevation of the front and rear portions of the oven taken from the control side; Fig. 10 is an enlarged fragmentary transverse sectional view on the line lli- IB of Fig. 9; Fig. ll is an enlarged fragmentary transverse sectional View taken on the li'ne l i-H of Fig. 9; Fig. 12 is an enlarged fragmentary elevation of one of the observation and access doors in the control of the oven; Fig. 13 is a transverse sectional View on the line 13-13 of Fig. 12; Fig. 14 is a fragmentary sectional View taken on the line M-IA of Fig. 9; and Fig. 15 is a fragmentary View of one of the roller-supporting adjustable plates.

As illustrated in the drawings, my inventi n comprises an oven composed of a series of but not identical, units l, 2 and 3, having raobeted end edges abutted together to form lap joints Il around the entire periphery or the oven and forming a tunnel which is4 divided longitudinally, along at least a portion of its length. by a horizontal partition 5, to form an upper pass E and a lower pass l.

Each oven unit is composed of a pair of sirnilar, horizontally disposed and vertically spaced panels 8 and and a pair oi similar, vertically disposed and horizontally spaced panels As shown, one of the panels 9 is of different thickness from the other panels 9 but the relative thickness oi the panels is dependent upon the external conditions to which the panels may be exposed. The panels 9 of the terminal unit 3 are preferably oi less height than the corresponding panels e of the units i and 2 so that the bottom lap of the baking band may pass beneath the bottom ci the terminal unit 3 as hereinafter described.

Each top and bottom panel il is composed of sets of plates il), H and I2 secured together by bolts I3 and nuts ill, as illustrated in Fig. l0 so that the bolts do not transmit heat through the panels. The plates lil, Ii and i2 are all of substantially the same length, but the plates i i are onset lengthwise with respect to the transverse centerline of the plates Il?, and the plates ii.l are oiset lengthwise with respect to the transverse centerline of the plates ii so as to form parallel, reversely extending ilights oi steps at the opposite ends of each panel. The steps of endwise abutted panels overlap one another to forni a joint which may be sealed by a strip of compressible asbestos paper l5 laid between the surfaces of the joints, as shown in Fig. ll.

The plates i! are of lesser width than the plates I9, and the plates l2 are of lesser width than the plates il, and rall the plates it?, l! and i2 are centered with respect to the longitudinal centerline of the plates lil so as to forni converging nights of steps along the lateral, longitudinally extending opposite edges of the panels B.

Each side panel. 9 is of the same length, but preferably of lesser width, than a panel 8 and is generally similar in construction thereto. That is, each panel Q is composed of sets of plates iii and Il and one or more plates i8, which are bolted together by bolts i3 and nuts lli, as indicated in Fig. l0. The plates le, il and i@ are all of the sarne length, but the plates il are offset longitudinally from the transverse centerline of the plates It and the plate or plates is are offset longitudinally from the transverse centerline of the plates il so as to form parallel, but oppositely extending flights of steps at the opposite ends or the panel. The steps of end abutted panels overlap one another to forni joints which may be sealed by a strip of compressible asbestos i3, as illustrated in Figs. 2 and 11.

The plates il are of less width than the plates i6 and the plates it are of less width than the l plates il, but the plates i5, il and i8 are all centered with respect to the longitudinal centerline of the plates it so as to forni converging nights of steps along parallel edges of the panels 3.

A series or panels B are laid, in interlocking rclation, directly on a iloor or solid 1foundation 2i ci substantially inexpansible material, such as concrete, between a pair of parallel Lashaped steel beams 22 extending externally the iull length of the units i and 2, the joints being sealed by compressible asbestos strips i5. Two rows of abutted panels il are then stood on the lateral longitudinally extending steps of the panels S the joints being sealed by cornpressible asbestos strips i9 and Zt. rlhe side panels are held in position by the upwardly projecting ilanges of the bearns 22 and by top tie rods 22 completely enclosed by the panels.

A row oi inverted, abutted panels S are laid on the tops oi the rows of panels S the joints between the abutted panels 8 Vbeing sealed by compressible strips i5 and the joints between the panels 8 and Si being sealed by coinprcssible strips 2?.

The panels 8 and 9 are rnade of asbestos, preferably Marinite boards, or similar material of very low thermal expansibility and the longitudinal expansibility of a unit is less than the compressibilit -1 ci the sealing strips between adjacent units, so that there is no cumulative ex pansion of the units to change the overall length of the tunnel as a result oi the heating or cooling thereof. Marinite is a combined structural and insulating material composed of asbestos (amosite) fibre, silica. sand and an inorganic binder, such calciurn silicate. The interior oi the tunnel is devoid of any longitudinal extending metal bearns or other thermally expansibie members attached to the units so tnat no stresses or strains are imparted thereto.

and moisture is exhausted from the pass i5 by forming an upwardly tapering or arched recess 2@ forming a chamber in the upper panel 8 of certain of the units as indicated in Figs. 2 and 5. Exhaustion takes place from such chambers in uniformly spaced units throughout the range or baking, from one unit of each four units. The recess iii?, in the upper panel t of each such unit has a mouth extending substantially the Width of the tunnel and covered by a grid 2li containing uniformly spaced apertures 2li of uniform area. The areas of these apertures aggregate approximately the minimum cross sectional area of an exhaust port 2li extending through the panel t at substantially the center thereof. The arched formation insures a smooth now of air to the port 25 and provides suiiicient structural strength `for the support of exhaust manifolds 2%; which communicate with the ports 2li through branches 2t. Y

Exhaustion of from various areas widthwise of the tunnel be varied, to meet abnorrnal conditions, by means of dampers 2l and 2l slidable laterally beneath the plate 2li containing elongated apertures 23 in the inner sections thereof and smaller apertures .2e in the outer sections thereof. The dampers 2l' and 2 may be manipulated from outside the oven by means of pull rods Se and Si. By means of these pull rods each damper may be positioned so that all of its apertures 2t and 2Q register with apertures in the plates 2li or may be so positioned that the apertures register with apertures in the plate 2&3 but the apertures 29 do not register with the apertures in the plate 24', or may be so positioned that none of the apertures in a damper register with an a-perture in the plate 2li.

Each exhaust port 25 communicates with one of the exhaust manifolds 2t and each manifold is exhausted by a suction fan 33 driven by a motor 34 and discharging to atmosphere through a stack 35. The sections of each manifold 2B increase in cross-sectional area between the more remote vents 25 and the exhaust fan 35 proportionately to the area of each additional vent 25 communicating with the manifold so that substantially the same suctin is normally applied to all the units l and 2. The moisture laden air rises to and flows along the unobstructed top of the tunnel to the nearest chamber 24 so that no eddies or pockets of moisture laden air can accumulate.

The front of the oven is substantially closed by a panel 35, generally similar to a panel 9,

and having peripheral stepped edges 31 complementary to the stepped edges of the horizontal and vertical panels 8 and S forming the walls of the unit l.

The panel 3% contains the horizontal slots 38 and 39 for the ingress and egress of an endless belt 0r baking band 40. An intermediate plate 36' of the panel it may be made vertically adjustable to form a shutter for varying the size of the slot 3S.

The baking band i9 is looped on a takeup drum lll journalled on a carriage t2 which has downwardly beveled runners 132' riding on the ilaring flanges of spool-shaped, grooved rollers 43. The

inclined walls of the flaring iianges of the rollers d3 ride on the upwardly beveled rails M of a frame All. It will be noted that the spindles or Shanks of the rollers i3 are free from contact with the runners ft2 and rails fit and that the load is carried by substantially line contact between the beveled surfaces of the rollers and the complementary beveled surfaces of the runners and rails. Hence no skewing stress on the drum can prevent the free backward and forward movement of the drum carriage in response to expansion and contraction of the band.

The drum lll is biased toward the left (Fig. 2) by a weight i5 suspended from a cable 46 looped around a sheave Gil on the frame 44 and attached to a bridle 42" on the carriage 42 to ta-uten the band across its entire width. This mounting of the drum insures a constant tension on, and centering of, the baking band in the oven in all longitudinal positions of the drum. r*

As above noted, the side panels 9 of the unit (l do not extend down to the floor 2|, and the space between the bottom panel 8 of the unit 3 and the bottom panel 8 of the adjacent unit d is substantially closed by a panel 41, generally similar to a panel 9, and having stepped peripheral edges complementary to the stepped edges of the last unit 2 and the bottom panel 8 of thev unit 3.

The end of unit 3 is substantially closed by a panel d8, generally similar to a panel 9, and having stepped edges complementary to the stepped edges of the panels 8 and 9 of the unit 3. The panels l1 and d8 contain transverse slots H9 and for the ingress and egress of the endless belt d0. One of the internal plates 48 of the panel 48 may be made vertically adjustable to provide a shutter for varying the opening or the slot 5i).

The baking band 49 is looped around a driving drum 5| having a, shaft 52 journalled in frame bearings 531and provided with a pulley 54 through which the drum is driven by means of the driving belt 55 and motor 56.

The upper run of the endless belt 4I! is directly supported within the passage 6, by a series of cylindrical rollers 51 having peripheries engaging the band 40 throughout its entire width and trunnions 58 which pass through thimbles 59 and 69 in the panels 9 and are journalled in bearing 60 on blocks BI oi' the hollow beams 62 extending the length of the oven and mounted on pillars 63 resting partly on the feet of the beams 22. Preferably, a roller 51 is provided for each of the units l and 2 and the thimbles 59 are packed with thermally insulating disks 59a.

On leaving the unit 3, the upper run of the belt 40 passes over a roller 64 having trunnions 65 journalled in bearings 66 on an auxiliary frame 61. After passing around the drum 5|, the belt 49 passes over the auxiliary journalled rollers S8 and 69 and passes through the port 4 9 into the lower pass 1. The lower run of the belt 49 is supported, in the lower pass 1, by rollers 10 and by a group of rollers 1 i Each roller 19 has trunnions 12 which pass through thimbles 13 and 14 in the panels 8 and are journalled in bearings 15 of hangers 16 depending from the hollow beams G2. Since uniformity of level of the belt surface is less im.

portant in the lower return pass 1 than in the upper baking pass 6, fewer rollers are needed in'v the lower pass than in the upper pass and hence the rollers 19 need be provided in alternate units only.

The rollers 1l are provided with trunnions 11 which pass through enlarged slots in the panels 9 and are journalled in bearings xed to panels 18 of slides 18 on the opposite sides of the tunnel outside the panels il. The slides are lined with asbestos sheets 18". The slides 18 are longitudinally adjustable in slideways formed by the beams 22 and the frame members 19. The slides may be positioned longitudinally of the oven and held by set screws 19a in the frames 19. The rollers 1| are journalled at various heights in the slides 18 so as to form a downwardly inclined path for guiding the band du tangential-- slightly skew the rollers 1l as to press one end;

thereof more firmly against and tauten the slack side of the band and thereby make it run straight.

The upper pass 5 is heated by a series of. burners all disposed above the upper run of the' belt llt and containing lateral slits forthe emission of gas and air. A series of similar burners 89 are disposed below the upper run of the belt 39. Each burner 89, 85' has a leg 8| resting on a bracket 82 iixed to a panel 9 and each burner- Sl, 89 has a supply pipe 83 extending through a bushing 34 in the opposite panel 9. lEach of the bushings Bil may be provided with a peep? hole 85 and with an igniter 8E for lighting the burner. I

The upper row of burners 8l] is supplied with" fuel, preferably gas and air, through the tubes 81 communicating with a supply pipe 88 carriedM by hangers 89 on a beam 62 and the lower row of burners 90 is supplied with gas and air 7 through the tubesy or risers 90 whichv communicate with the supply pipe 9 i supported by hangers 92 on pillars 63. The supply pipes 88 and el are supplied with fuel through the valved pipes 92 endl-93 which communicate with the main S supported by the beam 95 running along the top of theoven. The temperature at various places in the pass 6 may be indicated by thermometers 9S.

The lower pass 'i may be, and preferably is, heated through a part only of its length, as, for instance, in a dozen units near the inlet end of the oven so as to pre-heat the belt All), particularly along the edges which tend to cool most rapidly. The baking band may be uniformly raised to a desired. temperature for thereception of products to be baked and which are deposited on the bandbetween the drum 4l and the port 38. This pre-heating may be effected by a series of burners S'fl positionedy beneath the lower run of the belt d, and similar in construction and mounting to the burners 89', and burners 9? may extend longitudinally of the oven along the edges of the band without transmitting any heat to the thermally expansible external frame members extending longitudinally oi the insulating tunnel.

It will. be understood that, in the operation of my improved oven, the burners, 8B, Si and t? will be lit by means of the respective igniters and the motor will be operated at ixed speeds or through pulleys of such relative size, as to translate the belt d through the thermally insulating tunnel at an appropriate speed to bake a desired product in a single transit on the band through the upper pass t. Ordinarily, when the product is a cracker or wafer, the speed and temperature will be set so as to bake the product in approximately three and a half minutes and while moving a distance of approximately three hundred feet, during which period approximately 195 pounds of water are evaporated.

The exhaust fans are operated during the preliminaryA heating of the oven and during baking and the dempers 2 and 2l will normally be positioned to effect registration of all 'the apertures therein with apertures in the plate 2i so that there will be a uniform exhaustion of moisture and heat across the entire width of the upper run of the belt and preferably across the entire top ofthe oven without the formation of any eddies or pockets.

The product to be baked is delivered to the exposed portion of the band at the inlet end oi the oven, and' during its travel through the thermally insulating tunnel, all of the products in a particular row are subject to the same baking condition at any particular instant but all the objects in a particular row may be subject to different baking conditions at different times in their transit through the tunnel by suitably adjusting the burners.

During the passage of the products through the last few units of the oven they may, if desired, be partially cooled by opening the insulated doors 9U of the ports 9! in certain panels 5.

The baked products are discharged through the port G and removed from the exposed section of the belt manually or mechanically before the belt section enters the lower pass 'l for pre-heating in preparation for the reception of a new supply.

The baking band may be either a closely or loosely woven wire mesh or a rolled thin. steel strip, either perforate or imperforate.

, Having described my invention, I claim:

I. A baking oven comprising an endless baking band, spaced drums' supporting and translating said band, rollers for supporting said band, each of said drums having a peripheral surface uniformly contacting said band across the width of the latter, slides having the rollers aforesaid journalled therein at different elevations to form an inclined path for said band to one of said drums, and means for adjusting said slides longitudinally for tautening the respective edges of said band.

2. A baking oven comprising an endless baking band, spaced drums supporting and translating said band, a carriage supporting one of said drums and having downwardly tapering runners, upwardly tapering rails beneath said runners, spoolshaped rollers between said runners and rails, said rollers having tapered flanges engaging said runners and rails and shanks spaced therefrom, and means for biasing said carriage. to tauten said band.

3. A baking oven comprising a pair of spaced drums one of which is movable relatively to the other, a baking band of thermally expansible material looped on said drums and having runs between them, a tunnel between said drums and having walls of insulating material of low thermal expansibility enclosing both runs ci said band, a pair of thermally expansible structural members extending substantially the entire length of said tunnel cn both sides thereof externally of said walls and shielded 'thereby from radiation or convection of heat from both runs of said band, and rollers each having trunnions supported both oi said members, each of said rollers having within the tunnel continuous peripheral surfaces uniformly contacting said band across the entire width of the latter.

e. A baking oven comprising a tunnel composed of units having top and bottom and side panels of low thermal conductivity, an upper row and a lower row of bushings in each of the said walls of the tunnels, two rows of rollers having trunnions passing through said bushings, and an endless baking band having an upper run moving along the upper row of rollers and a lower run moving along the lower row of rollers, thermally expansible structural members supporting said trunnions and extending lengthwise of said tunnel externally of said walls and.

shielded thereby from radiation or convection of heat, and drums having bigh'ts of said band looped thereon at the ends of said tunnel.

5. A baking oven comprising a multiplicity oi units abutted end to end to form a tunnel and an endless baking band traveling through said tunnel, each unit comprising a base composed of panels of low thermal conductivity with their lateral edges forming risers and treads of steps extending upward and inwardly; side panels having stepped lower edges resting upon said treads and lying against said risers, beams extending along the sides of said tunnel and shielded thereby from the heat from the lower run ci said band, rollers within said tunnel and having trunnions projecting through said side panels above and below the beams aforesaid, and bearings carried by said beams for supporting said rollers in direct contact with said band.

6. A baking oven comprising a long tunnel composed of a multiplicity of units ci low 'thermal conductivity, a horizontal partition within said tunnel and extending along a substantial portion thereof, an endless baking belt having sections traveling in opposite directions through said tunnel above and below said partition, means for tau* 'ig the belt section below said partition, hea mg elements spaced along substantially the e len' th of the tunnel above the partition, elei spaced along a portion only7 of the tunnel b -low the partition and pre-heating the taut section oi said belt before the entry7 therei the nnel above the partition, said last named heating elements extending along the edges of said beit Without extending across the middle thereof.

7. A baiting oven comprising an endless baking band, spaced drums supporting and translating said band, a tunnel surrounding said band between said drums and having a roof containing spaced exhaust chambers extending crosswise oi said band beyond the edges thereof, the tops oi said exhaust chambers forming arches, suction pipes supported by said arches and communicating with ports in the top of said chambers, each of said arches extending at least the full Width of said band and having surfaces symmetrically inclined upward from the sides of said tunnel substantially tc said suction pipes, and grids having substantially uniformly spaced apertures extending across the bottom oi said chambers.

8. A baking oven comprising an endless baking band, spaced drums supporting and translating said band, a tunnel surrounding said band between said drums and having a roof containing spaced exhaust chambers extending crosswise oi said band beyond the edges thereof, suction pipes communicating with ports in the top of said chambers, each of said chambers having surfaces inclined continuously upward from beyond the edges of said band to substantially the port in the top oi said chamber, and grids having substantial ly uniformly spaced apertures extending across the bottom of said chambers, the aggregate area of the apertures in a grid approximating the area of the exhaust port complementary thereto.

9. A baking oven comprising an endless baking band, spaced drums supporting and translating said band, a tunnel surrounding said band loetween said druins and having a roof containing spaced exhaust chambers extending crosswise of said band beyond the edges thereof, suction pipes communicating with ports in the tops of said chambers, grids having substantially uniformly spaced apertures extending across the bottoms of said chambers, and an apertured damper cornplementary to each of said grids and movable transversely to the length of said oven for regulating the flow of air through such grid.

10. A baking oven comprising an endless baking band having a baking surface, spaced drums supporting and translating said band, cylindrical rollers each having a peripheral surface uniformly contacting said band continuously across the width of the latter for supporting it between said drums, a tunnel surrounding said band between said drums and having a roof composed of asbestos panels forming a iiat ceiling over the major area of the baking surface of said band, certain ci said panels containing upwardly tapering recesses forming chambers each having a mouth extending crosswise oi the tunnel at least the full width oi the baiting band, the mouths or" said recesses being spaced from one another longitudinally of the tunnel a d tance greater than the breadth longitudinally ci the tunnel of any mouth aforesaid, an xhaust port at the top of each of said recesses, a grid covering the mouth of each oi said recesses, each grid ccntaining spaced apertures.

l1. A baking oven comprising an endless baking band having a baking surface, spaced drums sup-- porting and translating said band, cylindrical rollers each having a peripheral surface uniformly contacting said band continuously across the width of the latter for supporting it between said drums, a tunnel surrounding said band between said drums and having a roof composed of asbestos panels forming a iiat ceiling over the major area of the baking surface oi said band, certain oi said panels containing upwardly tapering recesses forming chambers each having a mouth extending crosswise of the tunnel at least the full width of the baking band, the mouths of said recesses being spaced from one another longitudinally of the tunnel a distance greater than the breadth longitudinally of the tunnel of any mouth aforesaid, an exhaust port at the top of each of said recesses, and a grid covering the mouth of each of said recesses, each grid containing spaced apertures whose aggregate areas approximate the minimum cross sectional area of the exhaust port in the top of the recess whose mouth is covered by said grid.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 838,270 Peters Dec. 1l, 1906 1,000,974 Anderson Aug. 22, 1911 1,491,689 Gantvoort Apr. 22, 1924 2,143,525 Salerno Jan. 19, 1939 2,149,537 Morton Mar. 7, 1939 2,224,634 Holtzman et al Dec. 10, 1940 2,256,003 Patterson Sept. 16, 1941 2,327,727 Loose et al Aug. 24, 1943 2,499,934 Sullivan et al Mar. 7, 1950 

